Deutsch and Glavan have prepared cationic lipophilic complexes of technetium-99m that are useful as negative heart imaging agents. The agents that they have prepared accumulate in the normal heart and visualize an infarct as a cold area on a relatively hot background of normal tissue.
The expression "cationic lipophilic complexes of technetium-99m" is used by Detusch and Glavan to describe complexes of technetium-99m having lipophilic ligands and an overall cationic charge. Their preferred complexes are described by the formula EQU [(L).sub.2.sup.99m Tc(X).sub.2 ].sup..sym. X.sup..crclbar., I
wherein each L represents the same or different lipophilic ligand strongly chelating for a technetium-99m cation, and wherein the three X's are the same or different monovalent anionic ligand.
The above-described complexes are prepared by Deutsch and Glavan using the following procedure. The ligand and technetium-99m (in the form of pertechnetate ion or reduced derivative thereof) are first complexed in a mono- or biphasic system. A large (preferably greater than ten fold) excess of lipophilic ligand over technetium is used. The resulting complex is isolated and purified using standard chromatographic techniques. Finally, the "purified" complex is dissolved (or suspended) in a pharmacologically acceptable administration vehicle. Among the vehicles suggested by Deutsch and Glavan are saline, 50/50 ethanol/saline, vehicles wherein the concentration of ethanol is varied, vehicles wherein ethanol is replaced by other organic portions such as propylene glycol, glycerol or dimethyl sulfoxide, or vehicles based on solubilization of the radiopharmaceutical in micelles.